summon: raise SummonError appropiately

dvc/api.py

@@ -12,8 +12,9 @@ except ImportError:
 import ruamel.yaml
 from voluptuous import Schema, Optional, Invalid, ALLOW_EXTRA
 
-from dvc.utils.compat import urlparse, builtin_str, FileNotFoundError
+from dvc.utils.compat import urlparse, builtin_str
 from dvc.repo import Repo
+from dvc.exceptions import SummonError, FileMissingError
 from dvc.external_repo import external_repo
 
 
@@ -128,19 +129,21 @@ def _get_object_from_summoners_file(name, path):
     Given a summonable object's name, search for it on the given file
     and bring it to life.
     """
-    with open(path, "r") as fobj:
-        try:
+    try:
+        with open(path, "r") as fobj:
             content = summon_schema(ruamel.yaml.safe_load(fobj.read()))
             objects = content["objects"]
             return next(x for x in objects if x["name"] == name)
-        except FileNotFoundError:
-            pass  # XXX: No such YAML file with path: '<path>'
-        except ruamel.yaml.ScannerError:
-            pass  # XXX: Failed to parse YAML correctly
-        except Invalid:
-            pass  # XXX: YAML file dosen't match with the schema
-        except StopIteration:
-            pass  # XXX: No such object with name: '<name>'
+    except FileMissingError as exc:
+        # XXX: Prints ugly absolute path.
+        raise SummonError("No such YAML file with path: '{}'".format(path))
+    except ruamel.yaml.YAMLError as exc:
+        raise SummonError("Failed to parse YAML correctly", exc)
+    except Invalid as exc:
+        # XXX: Doesn't point out the error.
+        raise SummonError("YAML file dosen't match with the schema", exc)
+    except StopIteration:
+        raise SummonError("No such object with name '{}'".format(name))
 
 
 def _invoke_method(call, args, path):

dvc/exceptions.py

@@ -353,3 +353,7 @@ class PathMissingError(DvcException):
             " neighther as an output nor a git-handled file."
         )
         super(PathMissingError, self).__init__(msg.format(path, repo))
+
+
+class SummonError(DvcException):
+    pass

tests/func/test_api.py

@@ -13,6 +13,7 @@ from dvc.main import main
 from dvc.path_info import URLInfo
 from dvc.remote.config import RemoteConfig
 from dvc.utils.compat import fspath
+from dvc.exceptions import SummonError
 from tests.remotes import Azure, GCP, HDFS, Local, OSS, S3, SSH
 
 
@@ -151,14 +152,18 @@ def test_summon(tmp_dir, erepo_dir, dvc, monkeypatch):
     different_objects["objects"][0]["summon"]["args"]["x"] = 100
 
     dvcsummon_yaml = ruamel.yaml.dump(objects)
-    non_canon_yaml = ruamel.yaml.dump(different_objects)
+    different_yaml = ruamel.yaml.dump(different_objects)
+    invalid_yaml = ruamel.yaml.dump({"name": "sum"})
+    not_yaml = "a: - this is not a valid YAML file"
 
     with monkeypatch.context() as m:
         m.chdir(fspath(erepo_dir))
 
         erepo_dir.dvc_gen("number", "100", commit="Add number.dvc")
         erepo_dir.scm_gen("dvcsummon.yaml", dvcsummon_yaml)
-        erepo_dir.scm_gen("non-canon.yaml", non_canon_yaml)
+        erepo_dir.scm_gen("different.yaml", different_yaml)
+        erepo_dir.scm_gen("invalid.yaml", invalid_yaml)
+        erepo_dir.scm_gen("not_yaml.yaml", not_yaml)
         erepo_dir.scm_gen(
             "calculator.py",
             "def add_to_num(x): return x + int(open('number').read())",
@@ -169,4 +174,16 @@ def test_summon(tmp_dir, erepo_dir, dvc, monkeypatch):
 
     assert api.summon("sum", repo=repo_url) == 101
     assert api.summon("sum", repo=repo_url, args={"x": 2}) == 102
-    assert api.summon("sum", repo=repo_url, fname="non-canon.yaml") == 200
+    assert api.summon("sum", repo=repo_url, fname="different.yaml") == 200
+
+    with pytest.raises(SummonError):
+        api.summon("sum", repo=repo_url, fname="not-existent-file.yaml")
+
+    with pytest.raises(SummonError):
+        api.summon("non-existent", repo=repo_url)
+
+    with pytest.raises(SummonError):
+        api.summon("sum", repo=repo_url, fname="invalid.yaml")
+
+    with pytest.raises(SummonError):
+        api.summon("sum", repo=repo_url, fname="not_yaml.yaml")